a rare type of leukaemia; near-haploid patients tend to be children or teenagers; slight excess of females

Prognosis

generally short complete remission duration and poor prognosis, although long survivors have been reported

Cytogenetics

Cytogenetics Morphological

near haploidy is usually defined as <30 chromosomes; typically the abnormal clone has 23-28 chromosomes; the pattern of chromosome loss in near-haploidy is not random as there is preferential retention of two copies of chromosomes 6, 8, 10, 14, 18, 21, and the sex chromosomes; in addition to the haploid clone it is common to see a normal diploid clone and a cell line with double the near-haploid number of chromosomes, resulting in hyperdiploidy; occasionally the near-haploid clone is hard to detect resulting in apparent hyperdiploidy; the hyperdiploid cells however tend to have 2 or 4 copies of chromosomes and can thus be distinguished from typical >50 hyperdiploid ALL; the distinction is important as near-haploidy defines a rare type of childhood ALL associated with short median complete remission duration and poor prognosis

Additional anomalies

occasional structural chromosome abnormality

Bibliography

Acute lymphoblastic leukemia with a hypodiploid karyotype with less than 40 chromosomes: the basis for division into two subgroups.